Magneto generator



May 15, 1951 H. E. BRUNELLE ETAL MAGNETO GENERATOR Filed 001;. 11, 1949 nip-nu Henry Luther 5. Molde,

Irwvencors:

E. Bvunelle,

MW heir Attorney Patented May 15, 1951 UNITED PATENT QFFICE Lu e l sll l e M nt video Minn, assis prs tolG'eneral Electric. Company, a corporat on of New York Application Octoberll, 1949, Serial-No.120fl52 ll claims. 1

This invention relates to magneto generators, more particularly to breakerless magneto generators of the type described and claimed in U. S. patent 2,446,446 to Warginet al., dated August 3, 1948.

In ignition systems which utilize two voltage impulses in connection with a voltage doubler circuit to fire a single spark plug, the timing of the voltage impulses is very important. 'Ihisis particularly true in cases, such as inaircrait engines, where it is-necessary to operate a large number of spark plugs from a single distributor. In such cases the space between distributor electrodes and the time between spark plug discharges are both limited, making it difiicult to insure that two complete charges are generated before the time for discharge is reached. It is an object of this invention to provide a magneto generator which insures that two complete charges are generated before the time for discharge is reached.

Most intermittent and alternating polarity magneto generators now in use provide voltage impulses at regular intervals dependent upon the speed. It is a further object ofthe present invention to providea magneto generator which produces Voltage impulses at irregular intervals.

In carrying out. our invention in one form, we provide an alternating polarity magneto generator of the inductor type in which magnetic flux alternates in stator polar portions due to the changing position of the rotor. Both the stator and rotor are provided with flux conducting teeth. The teeth on the rotor are regularly spaced and of identical dimensions, but the teeth on alternate stator poles are of unequal width. The unbalanced alternating flux produced by the rotation of the rotor results in alternating voltage impulses in the voltage output coils of the magneto separated by different timeintervals for one polarity than for the other. This alter,-

nating voltage may be applied to a voltage doubler circuit in a breakerless type ignition system. The voltage doubler circuit, inturn impresses the aggregate of two complete charges for each spark plug operation on transformer type spark plugs through an air-gap type distributor. The use of a magneto generator which produces voltage impulses at irregular intervals insures that two complete charges are generated before each spark plug discharge because such a generator makes it possible to generate two complete charges in a shorter interval than would otherwise be the case.

For a clearer and more complete understanding of ourinvention, reierence Sh uld behad to the accompa ngdraw n n whi h F ,1 i a ch matic ia am of,apr i r edembodiment of the invention; Fi 42.1.5 p rtia s h ma diaram lust at n h a net era o in a different rotational position than Fig. 1; while in F gs. B LBB d..3 ther r sh wn curves to fa li ate unde tand n ofth ve t nli rr na o Fla .lo h drawin ther is .-..s. a l re ke es ni i system. o th ow n on hi h r uen type, wh r n th el .i. ro e i su pl ed y ama neto en rator, ndica e generally a T s sni ion stem is d fine in u co ns i sion l ap licaenfi N 8.8 7 h cni as igned-t0 the assignee of the present invention. {The magneto generatoris of the inductor typeand comprises a -rotary member 2 mounted on a drive shaft 3, which may be driven by any suitable means (notshown). The rotor i2 is-formedof magnetic material and is preferably of laminated construction, the rotor being provided ,with a plurality of circumferentially spaced teeth 4.

Extending around the rotor member Us a stator member comprising four spaced arcuate pole pieces 5, 5, l and 8. Stator pole pieces 5 and r1 are provided with a plurality 0f uniform inwardly extending :projections or teeth :9, while f pole pieces 5 and .tareprovided with a plurality of uniform inwardly extending teeth The stator teeth 9 and It cooperate with therotor teeth 4i11establishing different low reluctance magnetic circuit paths through the rot or and the stator pole pieces as is subsequentlyldescrihed in-detail.

The magneto, generator I is provided withtwo output coils ii and 12 which are mounted, respectively, on magnetic core members l tand il l. As illustrated in the drawing, the core member 13 is arranged magnetically tointerconnect the stato-rpole pieces 5 and 5, while core member i4 is arranged magnetically to interconnect stator pole pieces 1 and 8, the core membersl lt and HI being located on diametrically opposite sid es of the stator.

E he m s fi resen ing a ou c .0 masnetic flux which is periodically directed through th 9 m m s- 3 an l 4 n opp s te dir ctions upon the rotation of the member '2, there are provided two permanent magnets 15 and .15 located on diametrically opposite sides .of the stator. Aeshown, thepermanentlmagnet i5 is forms a magnetic link joining the two pole pieces.

The permanent magnet i6 is similarly arranged with its polar extremities abutting the adjacent ends of pole pieces and 8. This magnet also acts as a magnetic link, interconnecting these two pole pieces.

When the rotor 2 of the magneto rotates, the magnetic flux of the permanent magnets i5 and H5 is caused first to pass through the core members l3 and i l in one direction and then to be rapidly changed or switched so as to flow through the core members in the reverse direction, this alternate and rapid flux switching causing high induced voltages in the magneto output coils II and I2. This flux switching action of the magneto generator may be more easily understood by consideration of the low reluctance magnetic flux paths when the generator rotor is in each of the two different positions illustrated, respectively, in Figs. 1 and 2, of the drawing. When the rotor is in the position shown in Fig. 1 of the drawing, the rotor teeth t lie opposite the stator teeth Iii on pole pieces 8 and 8, whereby a low reluctance path is established interconnecting these two pole pieces diametrically across the rotor. At this time the teeth 9 of pole pieces 5 and I are out of registration with the rotor teeth so that the/flux path between these two pole pieces extending diametrically across the rotor is of relatively high reluctance. With the rotor of the generator in the position shown in Fig. 1, two low reluctance magnetic circuit paths are established, one of which may be traced as follows: The north pole of magnet IE, stator pole piece 5, core member l3, stator pole piece 6, diametrically across rotor member 2, stator pole piece 8 and back to the south pole of permanent magnet It.

When the rotor member 2 of the magneto generator rotates counter-clockwise an amount approximately equal to one-half the pitch of the rotor teeth, it occupies the position shown in Fig. 2 of the drawing. Referring to this figure, it will be seen that the rotor member 2 now establishes a low reluctance magnetic circuit path extending diametrically across rotor 2 between pole pieces 5 and I. At this time, rotor teeth 4 are out of registration with teeth Ill on stator pole pieces 6 and 8 so that the reluctance of the magnetic circuit path extending diametrically across the rotor between pole pieces 6 and 8 is relatively high. With the rotor in the position shown in Fig. 2, it will be noted that there are now two low reluctance magnetic paths whereby the magnetic flux of permanent magnets I5 and [5 threads the core members I3 and I 4 in the opposite direction from that shown in Fig. 1. One of these paths may be traced as follows: The north pole of permanent magnetic l5, stator pole piece 6, core member I3, stator pole piece 5, diametrically across rotor 2, stator pole piece I and back to the south pole of permanent magnet l5.

It will be noted from Figs. 1 and 2 that teeth 9 on stator pole pieces 5 and I are of greater width and, hence, of greater lateral cross-section than teeth ID on pole pieces 6 and 8, although all stator teeth are made relatively narrow for reasons which are given subsequently. The efiect of the difference in lateral dimensions of stator teeth 9 and I8 is to cause the magnetic flux through core members I3 and M to reverse at irregular intervals. This is due to the fact that rotor teeth 4 are opposite the wider stator teeth 9 in flux conducting relationship therewith for a greater interval than for the narrower teeth III, the radial air gap between rotor teeth 4 and the stator teeth being substantially the same in both cases. These irregularly spaced flux reversals produce alternating voltages in coils II and :3 having a different interval for one polarity than for the other, and these are used to advantage in our improved ignition system, as is explained below.

In order that the voltages induced in coils II and I2 may be as high as possible, the magneto rotor and stator teeth are so designed as to cause a very rapid change in the magnetic flux threading core members I3 and It, while the rotor member 2 is rotating. In order to accomplish this, the stator teeth 9 and It] are formed so that their width is small. In many cases, these teeth are made as narrow as possible, consistent with rigid construction and good manufacturing practices. In most cases, the stator teeth are appreciably narrower than the rotor teeth although this may not be the case in a relatively high speed magneto. While the expedient of making a single stator tooth narrow is desirable from the standpoint of obtaining a rapid flux change, it has the disadvantage that it reduces the longitudinal cross-sectional area of the stator tooth for an axial tooth length of any given value. The amount of magnetic energy required to be stored in the magnetic circuit of the magneto for each impulse determines the longitudinal cross-sectional area of the stator teeth and, therefore, in the conventional single-tooth stator construction this results in unduly long stator teeth, which is undesirable from the size standpoint. In the present arrangement, this difficulty is obviated by using a plurality of parallel stator teeth on each pole piece so as to provide a plurality of parallel flux paths across the air gap to the rotor. Thus, it will be noted that each of the stator pole pieces 5, 6, l and 8 is provided with three inwardly extending teeth. This arrangement permits the necessary amount of pole piece cross-sectional area to conduct the required amount of flux without necessitating undesirably long stator teeth. Obviously, more or less than three stator teeth per pole can be used, depending upon the number of rotor teeth being used and the amount of flux which is required in a particular case.

Referring now to the details of the illustrated ignition distribution arrangement, and more particularly to the distribution arrangement associated with magneto output coil 1 I, it will be noted that there is provided a pair of series connected storage condensers I? and I8 having a common terminal i9 which is connected to one of the output leads 26 of the coil H. The remaining terminal 25 of the condenser I7 is connected to the other coil lead 2i through a half-wave rectifier 22. The remaining terminal 23 of the condenser I8 is also connected to the coil lead 21 through a parallel circuit, including another half-wave rectifier 24. The magnetic and electrical polarities are so selected in connection with the current conducting directions of rectifiers 22 and 2% such that when the output of coil II is of one polarity, one of the condensers, say condenser II, is charged. Due to the action of re t fier-s 22 and 24, the next succeeding voltage impulse of opposite polarity of coil ll causes the condenser ill to be charged while the charge on condenser H is maintained. The polarities oi the condensers I? and it when charged are such that they are series aiding or additive, is, the voltage across terminals 2! and 23, when the condensers are fully charged, is substantially greater than across either condenser alone, and may be approximately twice as greatfor the illustrated case where two condensers were used.

In order to utilize this cascading arrangement advantageously, a circuit arrangement is provided whereby the voltage across the terminals 2! and 23 is periodically supplied by a distributor to various ignition circuits to fire spark plugs associated therewith. To this end, the terminal 25 is grounded, as indicated, and the terminal 23 is connected through a lead 25 to a rotary distributor, indicated generally at 2?. The distributor 21 is shown as comprising a plurality of stationary electrodes 28 which are arranged in a circular pattern. Cooperating with the stationary electrodes 28 is a rotary electrode or a distributor finger 29, which may be conveniently mounted on shaft 3, as shown, so as to be rotated in synchronism with the rotor member 2 of the magneto generator. The lead 25 is connected to distributor finger 29 through a slip ring arrangement 38 of conventional construction.

The ignition circuits illustrated by way of example in the drawing are of the so calied low tension high frequency type. For the purpose of simplicity, only one such circuit is illustrated in Fig. 1 for distributor 2?, but it willbe understood that in actual practice there is a separate ignition circuit and associated spark piug connected to each of the stationary distributor electrodes.

The ignition circuit shown in connection with the distributor 2? comprises a step-up transformer '35 having a primary or low voltage winding 32 and a secondary or high voltage winding 33. The high voltage winding 33 is connected to energize a spark plug 3 while the primary winding 32 is arranged to be periodically connected by the distributor 2.? to be energizedby series-connected condensers i? and it. In ignition systems of this type, a spark gap is used to initiate a high frequency oscillatory discharge in the primary circuit of transformer 32 and in illustrated arrangement the distributor used is of the air-gap type in which the required spark discharge takes place between the rotary distributor finger 29 and stationary electrodes 28. Thus, as distributor finger 2s rotates, it approaches to within arcing distance of the electrodes 28, but does not actually come in contact with them. An advantage of this type of ignition circuit lies in the fact that the distributor voltage may be of relatively low magnitude, for example, on the order of thee kilovolts, while the high voltage applied to-the spark plugs, which may, for example, be of the order or 18 kilovolts, is confined to the spark plug and the secondary winding of the step-up transformer. In order to eliminate corona loss to the surrounding atmosphere, stepup transformer 3i may be advantageously hermetically sealed in the spark plug, as will be well understood by those skilled in the art.

In ignition systems for radial engines, there must be provided compensation for timing irregularities which occur because of the use of articulated piston rods. In conventional ignition systems of the breaker type, this compensation is usually provided by properly selecting the angular relation of the cam lobes used to operate the breaker switch. In the present breakerless system, which is being used as an example, some other method must be used. Such timing compensation can be conveniently obtained in the present system by an appropriate circumferential spacing of thestationary distributor electrodes.

One of the principal advantages of this invention is that it permits such compensation, by means of angular adjustment of the stationary distributor electrodes, without detrimental effect on the operation of the ignition system. This will be more readily understood by reference to the curves of Figs. 3A, 3B, and 30 of the drawing. In Fig. 3A is shown a typical voltage wave resulting from a double volatge impulse from a magneto generator having voltage impulses occurring at regular intervals. In 331s shown a typical voltage wave of an ignition system employing a magneto generator constructed in accordance with the present invention. It will be noted from the curve of Fig. 313 that the voltage rises to the peak voltage required to completely charge the condensers earlier in the cycle than with the conventional generator and thereby allows an ample compensation and firing internal. In Fig. 3C, is shown the magneto generator flux wave corresponding to the output voltage wave of Fig. 3E.

The construction of the magneto generator I is such that it lends itself advantageously to the dual ignition arrangement illustrated in Fig. 1, wherein separate distribution circuits are as-- sooiated with each of the two output coils H and I2, the distribution circuit associated withv coil it having been described above. In orderto utilize advantageously the output of the sec-- ond magneto coil i2, there is provided another ignition distribution system which may be, as. shown, the same as the corresponding parts of the previous distribution system already described in connection with coil H. Parts of the second distribution system corresponding to those already described have been given corresponding reference numerals, except that the rotor 2 of the magneto generator is provided.

with 14 teeth and each of the distributors is provided with 14 stationary electrodes, making a total of 28 electrodes which are connected to 28 separate ignition circuits. With this arrangement, the shaft 3 which drives the magneto generator rotor and the distributor fingers 29 and 29 may be connected to the internal combustion engine so as to operate at one-half engine crankshaft speed. The characteristic of the magneto generator I is such that it inherently produces a number of impulses of alternating polarity in each of the coils H and i2 equal to twice the number of rotor teeth for each revolution of the rotor shaft. Thus, in the illustrated arrangement, there are 28 voltage impulses of alternate polarity induced in each of the coils ii and i2 for each revolution'of the drive shaft 3. Assuming the electrodes 28 and 28 to be equally spaced except for small angular irregularities to provide timing compensation, it will be clear from Fig. 333 that the magneto generator I produces two complete voltage impulses in the time interval required for each distributor finger to move from a position opposite one electrode to a position opposite the next adjacent electrode. Thus, the series-connected storage condensers are fully charged and ready for discharge through an ignition circuit each time a distributor finger moves opposite a stationary elec-.

trode. With this arrangement, it will be clear that the 28 ignition circuits are periodically and sequentially fired in pairs so that the system can be utilized to provide dual ignition for an engine having 14 cylinders.

It will also be readily understood by those skilled in the art that the system illustrated in Figs. 1 and 2 may be used to provide dual ignition for engines having an odd or even number of cylinders by providing a suitable number of teeth on the magneto rotor and suitable quantities of stationary electrodes for the distributors. Also, by utilizing only one of the output coils, provision may be made for single ignition for an odd or even number of cylinders. Similarly, provision may be made for more than two voltage impulses per firing interval, if desired.

While we have shown the improved magneto generator of our invention in a preferred form for use in a breakerless ignition system, it should be understood that it is not limited to use in such a system, but may also be used in many breaker type ignition systems.

It will be noted in Figs. 1 and 2 that the circumferential spacing between the adjacent encimost teeth 9 and ill on adjacent stator pieces is equal to approximately one and a half times the tooth-pitch of the rotor teeth, the distance being measured between the center lines of the stator teeth. It will be understood that this spacing may be any odd multiple of one-half the pitch oithe rotor teeth, that is, one-half, one and one-half, two and one-half, etc., as long as the rotor teeth 4 are out of register with stator teeth it when they are in register with stator teeth ii and vice versa.

An important advantage of the present invention is that it results in a considerably wider band of no electrical activity, as shown in Figs. 33 and 30, in which most values of distributor electrode compensation may be spanned without the spark discharge interrupting the voltage wave.

An additional advantage is that it stabilizes the level of the voltage to which the condensers are charged for each spark, since two complete voltage impulses are applied to the condensers for each spark.

By making all peak voltages uniform, this invention makes possible an increase in the altitude ceiling for ignition systems for air craft engines, since there is no Voltage higher than the desired minimum condenser charging voltage.

A still further advantage is that it reduces the amount of loss from the charge on the first condenser of a pair resulting from the first impulse, through the leakage of the rectifiers, because there is not as much time for decay before the second impulse occurs.

A still further advantage is that it makes more practical the use of a voltage multiplier electrical circuit in an ignition system, especially for use in engines of 14 or more cylinders in which the time for ignition of each spark plug and the angular spacing between distributor electrodes become critical.

While we have illustrated and described a preferred embodiment of our invention, modifications thereof may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, it should be understood that we intend to cover by the appended claims all such modifications as fall within the spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. In a magneto generator, a rotatable rotor member of magnetizable material having a plurality of circumferentiaily spaced teeth, a stator member of magnetizable material having an even number of spaced polar portions, and a plurality of substantially uniform spaced teeth extending radially inward from each of said polar portions forming an air gap with the teeth on said rotor member, the teeth on alternate ones of said polar portions having a rent cross section than the teeth on the intervening polar portions whereby the rotation oi said rotor member causes said rotor teeth to be adjacent said stator teeth in flux conducting relation therewith for different time intervals for the teeth on said alternate polar portions than on said intervening polar portions.

2. In a magneto generator, a rotatable rotor member of magnetizable material having a plurality of circumferentially spaced teeth, a stator member of magnetizable material having a plurality oi spaced polar portions, and a plurality of substantially uniform spaced teeth extending radially inward from each of said polar portions forming an air gap with the teeth on said rotor member, the teeth on said polar portions being constructed and arranged so that the rotation of said rotor member causes the rotor teeth to be alternately in and out of register with the teeth on alternate stator polar portions and simultaneously respectively out and in register with the teeth on the intervening stator polar portions, the rotor teeth being in register with the teeth on said alternate stator portions at irregular intervals with respect to the intervals during which the rotor teeth are in register with the teeth on the intervening stator polar portions.

3. In a magneto generator, a rotatable rotor member of magnetizable material, a stator member of magnetizable material having at least two polar portions thereon, a coil having a magnetizable core, said core being connected magnetically to said two polar portions, magnetizing means, and means responsive to rotation of said rotor member and including teeth of diiierent lateral cross section on the respective stator polar portions for periodically reversing at dissimilar time intervals the polarities of said polar portions whereby an alternating voltage having a longer interval for one polarity than for the other polarity is induced in said coil.

4. A magneto generator comprising a rotatable rotor member of magnetizable material having a plurality of uniform circumferential spaced salient teeth, a stator member of magnetizable material having an even number of spaced polar portions, a plurality of substantially uniform spaced teeth extending radially inward from each of said polar portions forming an air gap with the teeth on said rotor member, the teeth on alternate ones of said polar portions having a smaller arcuate dimension than the teeth on the intervening polar portions, means for magnetizing adjacent stator polar portions with opposite polarities, and a coil having a magnetizable core connected magnetically to opposite polarity portions of said stator member, adjacent stator polar members being spaced with respect to each other such that the teeth on said rotor member are alternately in register with the teeth on said alternate polar portions andv said intervening polar portions as the rotor member is rotated whereby alternating flux is produced in said magnetizable core through the coaction of the rotor and stator teeth, the alternate flux pulsations in one direction being of difierent time duration than the intervening pulsations in the opposite direction due to the difference in arcuate dimensions of the teeth on the stator polar portions.

5. A breakerless alternating polarity magneto generator comprising a rotor member of magnetizable material having a plurality of uniformly circumferentially spaced uniform salient teeth, a stator member of magnetizable material having an even number of spaced arcuate polar portions, a plurality of spaced substantially uniform teeth extending radially inward from each of said polar portions forming an air gap with the teeth on said rotor member, the arcuate pitch of the stator teeth on each polar portion being the same as the arcuate pitch of the rotor teeth, the teeth on alternate ones of said polar portions having a smaller arcuate cross section than the teeth on the intervening polar portions, means for magnetizing adjacent stator polar portions with opposite polarities, a voltage output coil having a magnetizable core connected magnetically to opposite polarity portions of said stator member, and means for rotating said rotor member, adjacent stator polar members being spaced with respect to each other so that the teeth thereon are separated by an odd multiple of one-half tooth pitch of the rotor teeth such that when the rotor teeth are adjacent the teeth on alternate stator polar portions the rotor teeth are out of register with the teeth on the intervening stator polar portions, whereby as said rotor member is rotated alternate low reluctance magnetic flux paths are formed through the rotor and stator members and alternating flux is produced in said magnetizable core, the alternate fiux pulsations in one direction being of different duration than the intervening pulsations in the opposite direction due to the difference in arcuate cross section of the teeth on alternate stator polar portions whereby there are induced in said coil alternating polarity voltage impulses having approximately equal potential values for both polarities but having a different time interval for one polarity than for the other.

6. An alternating polarity inductor-type magneto generator comprising a magnetizable rotor member having a plurality of uniform circum ferentially spaced salient teeth thereon, a magnetizable stator member having a plurality of polar portion thereon, each polar portion being provided with a plurality of uniform radially inwardly extending teeth forming an air gap with said rotor teeth, an output voltage coil having a magnetizable core connected to said stator member, magnetizing means, and means for rotating said rotor member, said stator teeth being constructed and arranged on alternate polar portions so that the said rotor teeth are adjacent the teeth on alternate stator polar portions in flux conducting relation therewith for dissimilar time intervals during said rotation, said rotor member being arranged to provide a plurality of flux paths therethrough, whereby as said rotation occurs an irregular alternating magnetic flux is produced in said magnetizable core and. alter nating voltage impulses are induced in said coil having approximately equal potential values for both polarities but having a different time inter- 7.

10 val following-aniimpulse of one polarity than an impulse Of the other polarity.

7. A breakerless magneto comprising a rotor having salient teeth, a plurality of spaced arcuate stator pole pieces disposed around said rotor, each of said stator pole pieces having a plurality of spaced substantially uniform teeth, the teeth on alternate ones of said stator pole pieces being of different cross section than the teeth on the intervening stator pole pieces, core members and permanent magnets alternately arranged between adjacent pole pieces, and output coils wound around said core members.

8. A breakerless magneto comprising a magnetiz-a-ble rotor having salient teeth, an even number of spaced arcuate magnetizable stator pole pieces disposed around said rotor, permanent magnets and magnetic core members interconnecting said stator pole pieces and arranged in alternate relation, a plurality of substantially uniform spaced teeth on alternate ones of said stator pole pieces cooperating with the teeth of said rotor, an equal number of substantially uniform spaced teeth on the intervening pole pieces of different cross section than the teeth on said alternate pole pieces, the teeth on said intervening pole pieces also cooperating with said rotor teeth, and an output coil encircling each of said core members for producing high voltage impulses.

9. A magneto generator comprising ,a magnetizable rotor member having salient teeth, two pairs of spaced arcuate m'agnetizable stator pole pieces disposed around said rotor member, each stator pole piece having a plurality of parallel teeth in flux conducting cooperation with and of narrower width than the teeth on said rotor member, the teeth on alternate ones of said stator pole pieces being of different lateral cross section than the teeth on the intervening stator pole pieces, alternately arranged permanent magnets and core members disposed between adjacent stator pole pieces, and an output coil magnetically encircling each of said core members for producing high voltage impulses of substantially uniform amplitude at irregular intervals.

10. A magneto generator of the inductor type comprising a rotor member formed of magnetizable material and having circumferentially disposed salient teeth, a stator member comprising a plurality of spaced arcuate pole pieces formed of magnetic material and disposed around said rotor member, each pole piece having a, pluralit of inwardly extending teeth cooperating with and spaced from said rotor teeth and being of narrower width than said rotor teeth, the teeth on each alternate pole piece being of different width than the teeth on the intervening pole pieces, a plurality of core members and a plurality of permanent magnets arranged to magnetically connect adjacent ends of said pole pieces, said core members and said magnets being alternately arranged around said pole pieces and said magnets being arranged with their polar extremities abutting adjacent pole pieces, and a coil associated with each core member, said stator and rotor teeth being so arranged that rotation of said rotor member causes two low-reluctance magnetic circuit paths to be alternately established for different time intervals through said rotor member, said stator pole pieces and said core members, whereby magnetic flux from said magnets alternately threads said core members in opposite directions causing alternating voltage impulses of approximately uniform amplitude but having a diiferent time interval for one polarity than for the other polarity to be induced in the coils associated with said core members.

11. A magneto generator of the inductor type comprising :a rotor member formed of magnetizable material and having circumferenti ally disposed salient teeth, a stator member comprising four spaced arcuate pole pieces formed of magnetizable material and disposed around said rotor member, a plurality of inwardl extending teeth of narrower width than said rotor teeth on each alternate stator pole piece cooperating with and spaced from said rotor teeth, a plurality of inwardly extending teeth on each of the intervening stator pole pieces equal in quantity to the number of teeth on each of said alternate pole 2 pieces, the teeth on said intervening pole pieces being spaced from and cooperating with said rotor teeth and being of narrower width than said rotor teeth but of different width than the teeth on said alternate pole pieces, a pair of core members and a pair of permanent magnets arranged to magnetically connected adjacent ends of said pole pieces, said core members and said magnets being alternately arranged around said pole pieces and said magnets being arranged with their polar extremities abutting adjacent pole pieces, and a coil associated with each core member, said stator and rotor teeth being so arranged that rotation of said rotor member causes two low-reluctance magnetic circuit paths of approximately equal reluctance to be alternately established HENRY E. BRUNELLE. LUTHER S. MOLDE.

REFERENCES CITED 5 The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date '30 1,183,286 Farny Ma 16, 1916 2,199,948 Brockway May 7, 1940 2,231,118 Guenther Feb. 11, 1941 2,272,625 Spengler Feb. 10, 1942 2,304,866 Wall Dec. 15, 1942 :5 2,446,446 Wargin Aug. 3, 1948 2,456,475 Wargin Dec. 14, 1948 2,508,524 Lang May 23, 1950 FOREIGN PATENTS Number Country Date 286,792 Italy June 22, 1931 

